A carpenter level, or spirit level as it is also known, is a commonly used tool by both craftsmen and homeowners for determining whether or not a surface is level, perpendicular to, or at a specified angle, relative to a datum or another surface. Levels are often used for a variety of other construction and decorative purposes, such as to determine whether walls are straight, shelves are level, and/or tiles are oriented at the desired angle. In operation, the level is placed against the surface in question by a user who can then view one or more bubble vials in the level to determine the position of the surface relative to a datum reference edge of the level. The user can then adjust the position of the surface in question as necessary, and again check the bubble vials in the level.
Levels come in a variety of sizes depending on the intended use. For example, often times smaller levels are used for checking the level of a decorative item such as a shelf, picture, or curtain rod. These levels may be only a few inches in length. On the other hand, longer levels which can sometimes extend a number of feet in length, are used for items having a greater surface area such as walls and floors. Depending on the task at hand, one or more levels, in varying sizes, may be required.